This document contains information from Chapter 2 of the prescribed textbook. The summary includes theories of aging, physical changes due to physical development, and sexuality.
Chapter 2: Physical Development and Sexuality
Introduction:
Aging is a continuous process
Most people peak with our muscle power, stamina, elasticity, agility, sensory
perception between 20-30 yrs.
There is however, a gradual decline, which usually only becomes noticeable after the
age of 40.
Golden rule: every person is unique and should therefore always be taken into account
as far as physical development is concerned.
Biological Theories of Aging:
Two general categories:
1. Programmed ageing theories: based on the assumption that ageing and death are built
into the genetic blueprint of all organisms.
life is genetically programmed
ageing is programmed to start after the reproductive ability ends.
molecular changes cause cells to age and lose their ability to divide and reproduce
changes in the hypothalamus eventually cause changes in the hormones that eventually
bring about ageing
loss of neurons in the brain cause ageing
a) Genetic programming theory: cells that constitute the body age in accordance with a
master genetic programme innate to every specific species.
- every species has its own programme of ageing and life expectancy.
Cell division:
There is a limit to the amount of times a cell can divide.
- 50 times for a young human.
As you grow older, your ability to divide cells decreases and therefore the cells
deteriorate until the person dies.
Telomeres: contain important enzyme called telomerase which is needed to replicate
the telomeres and thus the cell.
Telomeres are shortened with each cell division and the result is that telomeres
eventually become so short and contain so little telomerase that cell division cannot
continue.
2. Random error theory: based on the assumption that ageing reflects unplanned changes in
an organism over time.
explains ageing as a result from the accumulation of insults from the environment
which eventually reach a level of incompatibility with life.
, a) The wear-and-tear theory: argues that bodies age as a result of constant use.
decades of illnesses, injuries, and wear and tear cause damage to the cells, tissues and
organs.
eventually the body becomes progressively less able to repair damaged and worn out
components.
b) The Free Radical Theory: the nucleus of an atom is surrounded by a cloud of electrons
which could be described as elementary particles.
Free radical: electrons surround the nucleus in pairs, but occasionally an atom
loses an electron, leaving the atom with an “unpaired electron”.
described as scavengers that attack the structure of the cell membranes, thus
causing cellular damage and resulting dysfunction.
- linked to dementia, heart disease, cancer, cataracts and ageing spots.
c) The Cross-Linking Theory: with age, many body tissues become less flexible and
therefore less functional.
certain proteins cross link and produce molecules in such a way that they make the
body stiffer.
collagen: the more collagen there is the stiffer and less flexible and functional the
tissues become.
the number of cross-links increases as we from older because the muscles, arteries and
tissues become less flexible and effective the functioning of the body is negatively
influenced.
Specific Physical Changes:
The brain:
Weight of the brain begins to decline during middle-age (50) as a result of
deterioration and decrease in the number of neurons.
Blood flow to the brain starts decreasing
- implies a decrease in oxygen and glucose consumption often leading to a decrease
in cerebral metabolism and functioning.
Neurogenesis: the ability to repair and replace neurons in the brain.
People with higher levels of education show significantly less deterioration of the
cerebral cortex than those with less schooling.
The senses:
Vision:
- Best at approximately 20-40 yrs.
- Begins to deteriorate with the onset of middle-age.
- Gradual thickening of the lens, loss of lens elasticity and increased lens density and
the decrease in the ability to focus and maintain an image on the retina.
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